1,1

The exponent is congruent to 1 mod 3.

Table of n, a(n) for n=1..4.

Samuel S. Wagstaff, Jr. The Cunningham Project

(PARI) is(n)=my(t=10^n\9); ispseudoprime(t) && #bnfisintnorm(bnfinit(z^2+z+1), t) \\ Charles R Greathouse IV, Jun 13 2017

Cf. A004023, A003136.

Sequence in context: A172762 A203703 A068734 * A145851 A182374 A034207

Adjacent sequences: A216526 A216527 A216528 * A216530 A216531 A216532

nonn

V. Raman, Sep 08 2012

approved